# To W. T. Thiselton-Dyer   9 May [1878]1

Basset, Southampton.

May 9th.

(we return home on the 13th.)

My dear Dyer

I have given you & Hooker a rather long holiday, but now I want some aid badly.— I have written on separate slip of paper what I want.—2 I daresay I cd get the Cissus & Bignonia at Veitchs’, but Hooker told me to apply first to Kew.3 When at Kew a few months ago, Mr Lynch gave me fruits of 2 Cacteæ: we sowed the seed fresh & dried under various temperatures, but not one germinated. Of all the seeds of Cycas so kindly sent me only two cracked & these died.4 Why we failed I cannot imagine.

I have extreme wish to observe seedlings of Cacteæ & Cycas; if you have any seeds of latter, would you get Mr Lynch to raise a few for me & of some Cacteæ, & as soon as the earth cracks over the seeds or a vestige of a cotyledon appears, to despatch the pots to me.

I shall die a miserable, disgraced man if I do not observe a seedling Cactus. As for Cycas I have hardly any hope.—

We have been doing some really pretty work on radicles; but it is too long a story for you to read or for me to write. What trifles determine the success of experiments; Sachs missed a pretty little discovery solely by keeping his germinating beans too warm.— What magnificent work he has done on radicles.—5

I hope Mrs Dyer is going on well.—6

I saw a paragraph in Times from you about plants not turning to the Light for their profit, which has astounded me, & some time I must talk with you about this.7

Yours very sincerely | Ch. Darwin

P.S. I cannot resist telling you a little about the radicles. The apex is sensitive, & instead of turning to touching object like a tendril, it turns from it. The apex is so sensitive that if little squares (about $\frac{1}{20}$th of inch) of card & thin paper of exactly same size are fixed to opposite sides of apex, the radicle, (growing freely downward in damp air) bends always from the card side.— The apex of a radicle growing in earth tries to circumnutate, & thus prefers the earth on all sides; if one side is harder than the other the radicle will bend from this side, & thus it will discover with unerring precision the lines of least resistance in the ground.—8

Do not trouble yourself by answering this scrawl, but aid me if you can about the plants.— | C.D.

## Footnotes

The year is established by the address; CD was at Bassett, Southampton, from 27 April to 13 May 1878 (CD’s ‘Journal’ (Appendix II)).
The enclosure has not been found, but was evidently a list of seeds that CD wanted for his experimental work on the movement of cotyledons (seed-leaves). Joseph Dalton Hooker was director of the Royal Botanic Gardens, Kew (Thiselton-Dyer was assistant director).
Cissus is the genus of treebind; Bignonia is a genus of vines. The Veitch nursery had often provided CD with plants for his experimental work.
Richard Irwin Lynch was foreman of the propagating department at Kew. He had provided CD with several plant specimens for his experimental work on plant movement, as well as performing some experiments for CD (see, for example, Correspondence vol. 25, letters from R. I. Lynch, 25 July 1877 and the first and second letters of [before 28 July 1877]. Cacteae (a synonym of Cactaceae) is the family of cacti; Cycas is the only extant genus of the family Cycadaceae, a very ancient group of trees. CD had been sent seeds of Cycas in November 1877 and February 1878 (see Correspondence vol. 25, letter to J. D. Hooker, 8 November [1877], and this volume, letter to J. D. Hooker, 28 [February 1878]). According to the Outwards book (Archives, Royal Botanic Gardens, Kew), CD was sent seedlings of Cycas pectinata on 16 May 1878.
Julius Sachs had examined the movement of plant roots, in particular of the radical, or embryonic root, in ‘Ueber das Wachsthum der Haupt- und Nebenwurzeln’ (On the growth of primary and adventitious roots; Sachs 1873–4). Many of his experiments were performed with Vicia faba (broad or fava bean). CD also used V. faba for many of his experiments on the movement of the radicle, later published in Movement in plants.
Thiselton-Dyer’s wife, Harriet Anne, had given birth to their first child, Frances Harriet, on 9 April 1878 (Allan 1967 s.v. ‘Hooker pedigree’).
An article in The Times, 4 May 1878, p. 6, commented on the first of five lectures on vegetable morphology given by Thiselton-Dyer at the Royal Institution of Great Britain; the first lecture was on 30 April 1878. Thiselton-Dyer had reportedly said that light paralysed the protoplasm, making cells unyielding; the shaded side thus grew more readily, resulting in a bending toward the light.
CD devoted a chapter of Movement in plants to a discussion of the sensitivity of the apex of the radicle (ibid., pp. 129–200).

## Bibliography

Allan, Mea. 1967. The Hookers of Kew, 1785–1911. London: Michael Joseph.

Correspondence: The correspondence of Charles Darwin. Edited by Frederick Burkhardt et al. 27 vols to date. Cambridge: Cambridge University Press. 1985–.

Movement in plants: The power of movement in plants. By Charles Darwin. Assisted by Francis Darwin. London: John Murray. 1880.

Sachs, Julius. 1873–4. Ueber das Wachsthum der Haupt- und Nebenwurzeln. Arbeiten des Botanischen Instituts in Würzburg 1 (1871–4): 385–474, 584–634.

## Summary

CD wants some plants; asks Lynch to raise some Cactaceae for him. Observations on sensitivity and movements of radicle.

## Letter details

Letter no.
DCP-LETT-11499
From
Charles Robert Darwin
To
William Turner Thiselton-Dyer
Sent from
Bassett
Source of text
Royal Botanic Gardens, Kew (Thiselton-Dyer, W. T., Letters from Charles Darwin 1873–81: 119–21)
Physical description
6pp